BTW, I made my holes larger.
To avoid grinding down the welds to open mine back up, I took the muffler off (I'm a pro at this, now
) and used a piece of steel bar to make my holes oblong by going through the muffler inlet. I sharpened the tip of the bar to a chisel point, then used a 5lb sledge to hit the hole edge on with the chisel.
Rough estimate is that it's equivalent to three or four 1" holes per side, now. Sound is great and I'm satisfied now.
